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Publication numberUS6430150 B1
Publication typeGrant
Application numberUS 08/643,761
Publication date6 Aug 2002
Filing date6 May 1996
Priority date14 Feb 1996
Fee statusPaid
Publication number08643761, 643761, US 6430150 B1, US 6430150B1, US-B1-6430150, US6430150 B1, US6430150B1
InventorsMitsuhiro Azuma, Haim Kobrinski, Tsong Ho Wu
Original AssigneeFujitsu Limited
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Communication node, restoration method and communication network
US 6430150 B1
Abstract
In a telecommunication network, each node is provided with the same physical topology information relating to a physical construction of telecommunication paths included in the telecommunication network and with the same logical topology information relating to routing of telecommunication paths. When a failure occurs, restoration is effected by transmitting information relating to the failure that has occurred in the telecommunication network, throughout the network. Each node that receives the information relating to the failure determines alternative paths for bypassing the failure using the information relating to the failure, the physical topology information, and the logical topology information. Then service is switched to the alternative paths.
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Claims(16)
What is claimed is:
1. A restoration method in a telecommunication network in which each node is provided with physical topology information relating to a physical construction of telecommunication paths included in the entire telecommunication network and logical topology information relating to routing of telecommunication paths included in the entire telecommunication network, said restoration method comprising the steps of:
(a) broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the network;
(b) in each node that has received said information relating to the failure, determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and
(c) in each node, switching services to the alternate paths determined in step (b).
2. The restoration method as claimed in claim 1, further comprising the step of:
(d) initializing the step (b) when information relating to another failure is received while the step (b) is being executed, within a predetermined guard time, and executing the step (b) again allowing for the information relating to said another failure so that most up-to-date alternate paths are determined.
3. The restoration method as claimed in claim 1, further comprising the step of:
(e) exchanging between nodes data relating to said physical topology information and said logical topology information at predetermined timings so that the nodes are always provided with the same physical topology information and the same logical topology information.
4. A restoration method in a telecommunication network in which each node is provided with physical topology information relating to a physical construction of telecommunication paths included in the entire telecommunication network and logical topology information relating to routing of telecommunication paths included in the entire telecommunication network, said restoration method comprising the steps of:
(a) determining by computation in each node and storing in each node alternate paths adapted for typical failures prior to an actual failure;
(b) broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the network; and
(c) in each node switching services to the alternate paths determined prior to the actual failure in step (a).
5. The restoration method as claimed in claim 4, wherein said telecommunication network is an asynchronous transfer mode network based on a concept of virtual paths, and zero-capacity alternate virtual paths are set in step (a) as the alternate paths.
6. The restoration method as claimed in claim 1, further comprising the step of:
(d) identifying the type of failure by referring to the information relating to the failure and received by each node; wherein
alternate path selection adapted for the type of failure identified in step (g) is employed in step (b).
7. A telecommunication node provided with physical topology information relating to a physical construction of all telecommunication paths included in the entire telecommunication network and logical topology information relating to routing of said telecommunication paths included in the entire telecommunication network, said telecommunication node comprising:
first means for broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the telecommunication network;
second means for determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and
third means switching services in each node to the alternate paths determined by said second means.
8. The telecommunication node as claimed in claim 7, further comprising fourth means initializing a process in said second means when information relating to another failure is received while the alternate paths are being determined by said second means, within a predetermined guard time, and executing the process in said second means again allowing for the information relating to said another failure so that most up-to-date alternate paths are determined.
9. The telecommunication node as claimed in claim 7, further comprising fifth means exchanging between nodes data relating to said physical topology information and said logical topology information at predetermined timings so that the nodes are always provided with the same physical topology information and the same logical topology information.
10. The telecommunication node as claimed in claim 7, further comprising sixth means determining by computation and storing alternate paths adapted for typical failures prior to an actual failure; wherein
the process in said second means is not executed when a typical failure occurs, and said third means is used to switch services to the alternate paths determined prior to the actual failure.
11. The telecommunication node as claimed in claim 10, wherein said telecommunication network is an asynchronous transfer mode network based on a concept of virtual paths, and zero-capacity alternate virtual paths are set by said sixth means as the alternate paths.
12. The telecommunication node as claimed in claim 7, further comprising seventh means identifying the type of failure by referring to the information relating to the failure an receive by each node; wherein
alternate path selection adapted for the type of failure identified by said seventh means is employed by said second means.
13. A telecommunication network including telecommunication nodes each provided with physical topology information relating to a physical construction of telecommunication paths included in the entire telecommunication network and logical topology information relating to routing of telecommunication paths included in the entire telecommunication network, wherein each node comprises:
first means broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the telecommunication network;
second means determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and
third means switching services in each node to the alternate paths determined by said second means.
14. A restoration method in a telecommunication network comprising the steps of:
(a) providing each node with similar physical topology information relating to a physical construction of telecommunication paths included in the entire telecommunication network and providing logical topology information relating to routing of telecommunication paths included in the entire telecommunication network;
(b) broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the network;
(c) in each node that has received said information relating to the failure, determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and
(d) switching services in each node to the alternate paths determined in step (c).
15. A telecommunication node comprising:
storing means provided with physical topology information relating to a physical construction of telecommunication paths included in an entire telecommunication network and logical topology information relating to routing of telecommunication paths included in the entire telecommunication network, said informations being similar at each node in said network;
first means broadcasting information relating to a failure that has occurred in the telecommunication network, throughout the telecommunication network;
second means determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and
third means switching services in each node to the alternate paths determined by said second means.
16. A telecommunication network including telecommunication nodes, each said node comprising:
storing means provided with similar physical topology information relating to a physical construction of telecommunication paths included in the entire telecommunication network and similar logical topology information relating to routing of telecommunication paths included in the entire telecommunication network;
first means broadcasting information relating to failure that has occurred in the telecommunication network, throughout the telecommunication network;
second means determining alternate paths for bypassing the failure using said information relating to the failure, said similar physical topology information, and said similar logical topology information; and
third means switching services in each node to the alternate paths determined by said second means.
Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to networks using cross-connect units at telecommunication nodes, and more particularly to an automatic restoration method in a mesh network.

A synchronous transfer mode (STM) network and an asynchronous transfer mode (ATM) network capable of transmitting audio and visual data at a high speed have been in use in recent years to provide various services. One example of such a network is a mesh network in which telecommunication nodes provided with cross-connect units and telecommunication links are arranged in a mesh configuration.

Such a network should be configured so as to be capable of continuing to serve the user in the event of a failure. Continuation of services requires that a failure occurring in the network be automatically detected and telecommunication paths that enable bypassing of the failure be established. An automatic restoration method is an essential algorithm specifying a procedure for establishing the paths.

2. Description of the Prior Art

There are generally two types of automatic restoration methods proposed for mesh networks: the pre-planned restoration method and the dynamic restoration method. In the pre-planned restoration method, a configuration map specifying alternate paths is stored at each cross-connect unit.

In the event of a failure, alternate paths are set according to the configuration map. Hence, a high-speed restoration is possible. Information relating to the alternate paths is computed by the central Operation Systems and distributed throughout the nodes.

In the dynamic restoration method, each node is not provided with the above-described configuration map. In the event of a failure, nodes adjacent to the point of failure exchange restoration-related messages several times so as to find alternate paths.

However, the above-described conventional technology has the following problems. In the pre-planned restoration method, the process executed by the central Operation Systems to distribute the information relating to alternate paths to the nodes may be complex and lengthy. Further, when an additional failure (i.e., a secondary failure) occurs during the computation for finding alternate paths or during the distribution of the information, an updating computation and a distribution of the updated information to the nodes are required. Hence, the process required for the restoration becomes complex. Further, since each node is required to store the information in a memory, restoration capabilities for various failure scenarios are limited.

In the dynamic restoration method, restoration messages are exchanged between the nodes to search for alternate paths. Hence, a prompt restoration cannot be hoped for in comparison with the pre-planned restoration method.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a telecommunication node, a restoration method and a telecommunication network, wherein the aforementioned problems are eliminated.

Another and more specific object of the present invention is to provide a telecommunication node, a restoration method and a telecommunication network, wherein a prompt restoration is possible using a simple process.

The aforementioned objects can be achieved by a restoration method in a telecommunication network in which each node is provided with physical topology information relating to a physical construction of telecommunication paths included in the telecommunication network and logical topology information relating to routing of telecommunication paths, said restoration method comprising the steps of:

(a) transmitting information relating to a failure that has occurred in the telecommunication network, throughout the network;

(b) in each node that has received said information relating to the failure, determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and

(c) switching services to the alternate paths determined in step (b).

The aforementioned objects can also be achieved by a telecommunication node provided with physical topology information relating to a physical construction of telecommunication paths included in the telecommunication network and logical topology information relating to routing of telecommunication paths, said telecommunication node comprising:

first means transmitting information relating to a failure that has occurred in the telecommunication network, throughout the telecommunication network;

second means determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and

third means switching services to the alternate paths determined by said second means.

The aforementioned objects can also be achieved by a telecommunication network including telecommunication nodes each provided with physical topology information relating to a physical construction of telecommunication paths included in the telecommunication network and logical topology information relating to routing of telecommunication paths, wherein each node comprises:

first means transmitting information relating to a failure that has occurred in the telecommunication network, throughout the telecommunication network;

second means determining alternate paths for bypassing the failure using said information relating to the failure, said physical topology information, and said logical topology information; and

third means switching services to the alternate paths determined by said second means.

According to the restoration method, the telecommunication node and the telecommunication network of the present invention, restoration from failure is attained by using topology tables relating to the entirety of the network. Only information (message) relating to a failure needs to be exchanged for restoration. Therefore, the present invention realizes a high-speed restoration from failure with smaller volume of messages exchanged as compared with the conventional dynamic restoration method.

In further accordance with the present invention, reception of information relating to a failure is properly controlled so that cross-connection in a node is prevented from being executed in a transient state in which latest information relating to a failure has not arrived yet. Accordingly, it is possible to restore from failure using the latest topology information.

According to one preferred embodiment of the present invention, topology information is automatically updated so that the nodes in a network are provided with latest topology information relating to the entirety of the network which information is necessary for cross-connecting process executed in the event of a failure.

By executing, in each node, computation for finding alternate paths adapted for typical scenarios such as those involving a single link failure or a single node failure, a high-speed restoration from failure is realized.

According to another aspect of the present invention, restoration from failure can take place only by switching from a failed path to an alternate virtual path. Thus, a high-speed restoration is realized.

In further accordance with the present invention, alternate path selection most suitable for a failure type is employed so that a high-speed restoration is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:

FIG. 1A shows a telecommunication network and associated physical topology information;

FIG. 1B shows logical paths set and logical topology information in the telecommunication network shown in FIG. 1A;

FIG. 2A shows a telecommunication network having three nodes A, B and C;

FIG. 2B is a timing chart for the restoration algorithm of the present invention;

FIG. 3A is a timing chart explaining a guard time introduced in the restoration method of the present invention;

FIG. 3B is a timing chart explaining a guard time introduced in the restoration method of the present invention;

FIG. 4A shows a part of a process of updating topology information;

FIG. 4B shows another part of the process of updating topology information;

FIG. 5A shows a line restoration method and a node restoration method;

FIG. 5B shows a 2-hop restoration method;

FIG. 6 is a block diagram showing the construction of a telecommunication node according to an embodiment of the present invention;

FIG. 7 is a flowchart (1) showing the operation of the telecommunication node shown in FIG. 6;

FIG. 8 is a flowchart (2) showing the operation of the telecommunication node shown in FIG. 6; and

FIG. 9 is a block diagram showing the construction of a node in an ATM network, according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The basic algorithm for the restoration process according to the present invention is as follows. Each node in the network retains physical topology information relating to the physical construction of the telecommunication links included in the network and logical topology information relating to routing of paths formed in the links. In the event of a failure in the link or the node, the node adjacent to the location of the failure broadcasts a message to the other nodes in the network to indicate where the failure has occurred. Using the received message, each node performs computation for finding alternate paths so as to restore the telecommunication path for itself. By switching to the alternate paths determined as a result of the computation, a high-speed restoration based on a simple procedure is attained. More specifically, the aforementioned basic algorithm for the restoration process is composed of a broadcast phase, a computation phase and a cross-connection phase.

A description will now be given, with reference to FIGS. 1A and 1B, of the physical topology and the logical topology. FIG. 1A shows a telecommunication network and associated physical topology information. The telecommunication network shown has three nodes 1-3 and three telecommunication links L1, L2 and L3 connecting the nodes. The physical topology information indicates the physical construction of the links L1-L3, that is, the number of working (W) channels and the number of spare (S) channels formed on the links. In the example shown in FIG. 1A, L1 (6, 5) indicates that link 1 (L1) contains six working channels and five spare channels. Each of the nodes 1-3 keeps a table (physical topology table) as shown storing the physical topology information. Each of the nodes always keeps the physical topology information identical to each other.

FIG. 1B shows logical paths set and logical topology information in the telecommunication network shown in FIG. 1A. The logical topology information is routing information for the paths formed between the nodes. For instance, the logical topology information may indicate a path formed between the node 1 and the node 2 via the node 3. The logical topology information also indicate the number of channels (capacity) to be restored in the path. Each of the nodes keeps a table (logical topology table) as shown storing the logical topology information.

A description will now be given of the broadcast phase. In the event of a failure in a link or a node in the network, nodes adjacent to the location of the failure detect the failure. For instance, in the SONET network (the standard transport network in the United States), a node in the downstream of a failed location may receive an L-AIS (line-alarm indication signal) or an LOF (loss of frame) signal. A node in the upstream of the failed location may receive a FERF (far end receive failure) signal so as to recognize that a failure has occurred. The node that detected the failure prepares an alarm message and broadcasts the same in order to notify all the nodes in the network of the failure.

A description will now be given of the computation phase. The node that receives the alarm message executes computation (topology computation) for finding alternate paths using the topology information common to the nodes and stored in the physical topology table and the logical topology table. Consistent computation results (alternate paths) are obtained at each node, because common topology information of the network and a common computation algorithm for finding alternate paths are available and used in each mode. A known algorithm such as Dijkstra's algorithm may be used in the computation.

A description will now be given of the cross-connection phase. A node which has completed the topology computation starts the cross-connection depending on the result of topology computation so that services are switched from the failed path to the alternate path. Some nodes might not require cross-connection depending on the result of topology computation. Dynamic restoration protocols generally execute the cross-connection process synchronously in the final phase of the restoration. However, in the algorithm of the present invention, each node is able to asynchronously execute the cross-connection process. When cross-connection is completed by all nodes in the network, telecommunication along the restored path becomes possible.

FIG. 2A shows a telecommunication network provided with three nodes A, B and C, and FIG. 2B is a timing chart applicable to the restoration executed according to the above described scheme composed of three phases. In the example of FIG. 2A, a failure has occurred on the link between node A and node C. Node A and node C at the respective ends of the failed link detect the failure and enter a failure processing mode. Nodes A and C broadcast an alarm message for notifying the other nodes that a failure has occurred. The process executed so far concerns the broadcast phase.

Nodes A and C enter the computation phase after broadcasting the alarm message. Node B receives the alarm message broadcast from node A and node C. After recording the content of the message, node B broadcasts the alarm message. Thereupon, node B enters the computation phase. In the computation phase executed in nodes A-C, the topology computation is performed using the common topology information stored in the physical topology table and the logical topology table kept in each node. Consistent computation results (alternate paths) are obtained at each node, because common topology information of the network and a common computation algorithm for finding alternate paths are available and used in each mode.

Once the computation result is obtained in nodes A-C, each node enters the cross-connection phase. Nodes A-C switch services to the alternate path asynchronously according to the result obtained. Illustration of the alternate path thus determined is omitted in FIG. 2.

According to the above-described method, each node enters the computation phase after receiving the broadcast alarm message. Once the computation result is obtained, each node immediately enters the cross-connection phase. However, a node may receive a plurality of broadcast alarm messages in the event of a failure. If the plurality of alarm messages received relate to the same failure, no problem is created because the computation results obtained in accordance with the alarm messages are identical to each other. In the example shown in FIG. 2A, nodes A and C generate alarm messages which produce the same result in the topology computation. However, when a secondary failure occurs, for example, the plurality of alarm messages received successively by a node have different contents. In this case, the computation result obtained in accordance with the first alarm message received does not reflect the secondary failure, for example, that is, does not indicate the most up-to-date alternate path.

In order to avoid such an inconvenience, once the alarm message indicating the location of the failure has reached a node, the old computation process that has been executed in the node to find the alternate path is initialized. Thereupon, the computation for finding the alternate path is restarted using the old alarm message that the node received. In this way, it is possible to search for the most up-to-date alternate path. In addition, allowing for the possibilities of an additional alarm message arriving after the computation process is completed, it is necessary to wait at each node in the network until a guard time expires after the last topology computation is completed, before proceeding to the cross-connection phase.

FIGS. 3A and 3B are timing charts showing the above-described process. As shown in FIG. 3A, a node enters the computation phase after receiving an alarm message #1. Even if the computation is completed, the node does not execute a cross-connection until a guard time for the alarm message #1 expires.

Referring to FIG. 3B, a node enters the computation phase after receiving the alarm message #1, whereupon a guard time #1 is started. If another alarm message #2 is received in the process of computation, the computation is discontinued. A new computation allowing for the alarm message #2 is started. A new guard time #2 is started at the beginning of the new computation. When the guard time #2 expires, the node enters the cross-connection phase.

A description will now be given of how the physical topology table and the logical topology table maintained by each node are updated.

As has been described, the physical topology table and the logical topology table maintained by the nodes must have the common content. It is also necessary for the tables to reflect a secondary failure promptly. The physical topology is updated when the system is changed or a failure has occurred. This means that the physical topology is updated relatively infrequently. In contrast, the frequency that the logical topology is updated is higher than that of the physical topology. For instance, the logical topology must be updated whenever the path establishments are changed as requested by customers. Each node executes the process for updating the physical topology and the logical topology autonomously. The physical topology table and the logical topology table relating to the network maintained in each node are communicated from a node to all the other nodes in the network either periodically or at random intervals. In this way, the nodes can update the respective topology tables autonomously even when the OS issues an instruction that forces a change in the path establishments.

A description of the topology updating process will now be given using the logical topology as an example. FIGS. 4A and 4B show the process for updating the logical topology. Referring to FIG. 4A, the original working path goes from node A to node C through node B. To reassign the original path passing through node D instead of node B, the OS sends control messages to corresponding nodes A-D to notify them of the change. To update the logical topology table in each node after this path change, network nodes communicate with each other as shown in FIG. 4B. A similar process occurs in updating the physical topology table. The OS is not participating in the updating process.

If the entirety of the topology tables that nodes A-D maintain is to be confirmed by message exchanges between the nodes via the network, the information passed in the network amounts to an extraordinary volume. Accordingly, only the checksum (for example, the CRC checksum) of the physical topology table and the logical topology is transmitted instead of the whole table. Thereupon, nodes A-D make comparisons of the checksum transmitted. If the checksums are different from those received by other nodes, the node will then have to communicate with other nodes so that the same topology tables are maintained in the nodes.

A description will now be given of how the speed of the topology computation can be increased. As has been described, the topology computation is executed in the computation phase using a known algorithm adopted to search for the shortest path. Each node executes the computation using the physical topology table, the logical topology table and the alarm message received, according to the same algorithm.

It is possible for each node to execute topology computation adapted for different typical failure scenarios such as those involving a single link failure and a single node failure, before an actual failure occurs, using the physical topology table and the logical topology table maintained in each node. This computation (pre-computation) is done autonomously and the result thereof is stored in a predetermined part of the node. In this way, it is possible to restore services in the event of a typical failure without executing the computation. It is advisable to provide a guard time in this case, too. However, the guard time in this case may be shorter than when the pre-computation is not carried out.

A description will now be given of selection of the restoration method depending on the condition of a failure. Three types of alternate path selection may be employed: the line restoration method; the path restoration method; and the 2-hop restoration method. It is preferable that a restoration method most suitable for the condition of the failure be selected.

FIG. 5A shows the line restoration method and the path restoration method, and FIG. 5B shows the 2-hop restoration method. Referring to FIG. 5A, when a failure occurs between nodes 5 and 6, a path connecting nodes 6, 2, 3 and 5 and bypassing a failed link connecting nodes 5 and 6 at its ends is set according to the line restoration. The same failure as above is processed according to the path restoration such that an alternate path connecting nodes 1, 2, 3 and 4 is set in place of the path on the failed link, that is, the path connecting nodes 1, 6, and 4. Referring to FIG. 5B, a failure indicated by X and occurring in node 3 is processed by the 2-hop restoration method such that an alternate path is set between nodes 2 and 4 adjacent to node 3.

The line restoration method provides a faster restoration from a link failure than the path restoration. However, the line restoration cannot handle node failures. While the path restoration method can handle node failures, it takes longer to restore with the path restoration method than with the line restoration method. The 2-hop restoration method is a high-speed restoration method that includes features of these restoration methods and can handle node failures. However, the 2-hop restoration method cannot handle a plurality of successive failures. One of the above-described restoration schemes is used depending on the type of failure that has occurred.

FIG. 6 shows a node having the construction that realizes the restoration schemes described above. The node shown is connected to an STM or ATM network for transporting audio and image data, and to a maintenance message transmission line 34 for transmitting control messages and alarm messages from the OS.

The node shown in FIG. 6 comprises an alarm message detecting part 10, a failure type determining part 12, an alternate path computing part 14, an alternate path cross-connecting part 16, a cross-connection confirming part 18, a topology updating message detecting part 20, a physical topology maintaining part 22, a logical topology maintaining part 24 and a restoration preparing part 26. The restoration preparing part 26 includes an alternate path automatic computing part 28 and an alternate path storing part 30 and/or an alternate virtual path (VP) setting part 32.

The alarm message detecting part 10 detects an alarm message transmitted via the maintenance message transmission line 34 and passes the same to the failure type determining part 12. The failure type determining part 12 determines the location and type of the failure by referring to the information included in the alarm message, the physical topology information and the logical topology information. For example, the failure type determining part 12 determines whether or not the failure is a node failure or a link failure. In the event of a failure, a plurality of alarm messages are generated by nodes adjacent to the location of the failure. For example, in case of a link failure, two nodes generate the alarm message. In case of a node failure, as many as three nodes may generate the alarm message. In accordance with the plurality of messages, the location and type of failure are determined. Of course, it is possible to obtain information relating to the failure from a single alarm message. The number of messages involved in the determination depends on the construction of the network.

In response to the determination by the failure type determining part 12, the alternate path computing part 14 computes topology information to find alternate paths by referring to the physical topology information and the logical topology information. The computation is done using an algorithm such as Dijkstra's algorithm. On the basis of the result of computation, the alternate path cross-connecting part 16 issues an instruction for cross-connection to a cross-connect switch SW in the node so as to execute the actual cross-connection. After the node executes the cross-connection process, the cross-connection confirming parts 18 in the nodes work in cooperation so as to confirm whether or not the alternate paths set can operate properly.

The topology updating message detecting part 20 detects a control message from the OS and a topology updating message (for example, a message including a checksum) exchanged between nodes to update the topology information. The physical topology maintaining part 22 maintains the physical topology table as shown in FIG. 1A relating to the entirety of the network. The logical topology maintaining part 24 maintains the logical topology table as shown in FIG. 1B relating to the entirety of the network. The alternate path automatic computing part 28 of the restoration preparing part 26 pre-computes to find alternate paths adapted to typical failure scenarios involving a single link failure, a single node failure or the like, by referring to the physical topology table and the logical topology table. The alternate path automatic computing part 28 stores the computation result in an internal memory. There is no need to execute pre-computation adapted for all possible cases of single link failures and single node failures. The volume of pre-computation may depend on the storage capacity of the alternate path storing part 30 or the alternate VP setting part 32.

Upon detecting that the failure is a single node failure or a single link failure, the failure type identifying part 12 reads the computation result associated with the failure type from the alternate path storing part 30 or the alternate VP setting part 32 via the alternate path automatic computing part 28. The failure type identifying part 12 outputs the read result to the alternate path cross-connecting part 16.

It will be noted that telecommunication in the ATM network takes place using the virtual path (VP) connection. VPs with zero capacity can be preallocated as backups of working VPs on the basis of the result of the topology pre-computation. When a failure is detected and an alarm message is received by nodes adjacent to the location of the failure, a high-speed service restoration is realized by switching from the working path to the preset alternate virtual path. The aforementioned alternate VP setting part 32 stores the topology pre-computation result relating to zero-capacity alternate virtual paths adapted for typical failures.

In the STM network, a path is set by allocating data to time slots. Therefore, it is impossible to set virtual alternate paths. For this reason, in the STM network, the alternate path storing part 30 only stores the result of the topology pre-computation. When an actual failure occurs, the information relating to the alternate paths adapted for the failure type identified by the failure type identifying part 12 is read from the alternate path storing part 30 under the control of the alternate path automatic computing part 28. The read result is output to the alternate path cross-connecting part 16.

For example, the pre-computation is executed by the alternate path automatic computing part 28 immediately after a restoration from a failure or at regular intervals. Only when there is a difference from the old pre-computation result, the updated pre-computation result is reflected in the alternate path storing part 30 or the alternate VP setting part 32.

A description will now be given, with reference to FIGS. 7 and 8, of the operation of the node shown in FIG. 6. FIG. 7 is a flowchart of the process of restoration from a failure, and FIG. 8 is a flowchart of the process of restoration from a failure, wherein the topology pre-computation is executed.

Referring to FIG. 7, a determination is made in step (1) as to whether or not a failure is detected from an interruption of an optical signal or the like. If a failure is detected, the control is turned over to a process (step (3)) whereby an alarm message is sent to adjacent nodes. If no failure is detected, the control is turned over to a process (step (2)) for determining whether or not an additional message is received. Two types of messages may be received: an alarm message for warning of a failure on a transmission path; and a topology updating message that does not directly relate to a failure in the network. The type of the message received is determined and its content is passed to an associated message process. In case an alarm message is received, the control is turned over to an alarm message process described later. In case a topology updating message is received, the control is turned over to a topology updating process described later.

If a failure is detected or an alarm message is received from an adjacent node while step (3) is being executed, the alarm message that has been sent continues to be sent. The alarm message is sent to adjacent links other than the failed link and the link from which an alarm message is passed. No message that derives from the same factor is sent from a given node.

In step (4), the location of the failure is identified by referring to the alarm message received, and to the physical topology information and the logical topology information maintained in the node. In case of the link failure, nodes at the ends of the failed link send the alarm message. In case of a node failure, the location of failure is identified by receiving the alarm message from nodes adjacent to the failed node.

In step (5), a guard timer is started. During the guard time, an additional alarm that may be received during the topology computation is monitored. The time set is longer than the maximum time required for the topology computation so as to provide sufficient time for an alarm message indicating a failure to be transmitted throughout the network irrespective of the location of the failure in the network.

In step (6), topology computation is executed. The computation is executed based on the alarm message received, using an algorithm such as Dijkstra's algorithm or the like. In this computation, the physical topology table and the logical topology table are used.

In step (7), a determination is made as to whether or not an additional alarm message is received during the computation. If an additional alarm message is received, the control is returned to the process for identifying the failure type. If no additional alarm message is received, the control is turned over to a step (8) for determining whether or not a guard time has expired.

If it is found in step (8) that the guard time set in a guard timer has not expired, the control is returned to step (7). If the guard time has expired, the control is turned over to a step (9).

In step (9), a cross-connecting process for switching to alternate paths is executed in each node, in accordance with the result of the topology computation. In step (10), a confirmation is made after the cross-connecting process as to whether or not the alternate paths are properly set.

A description will now be given of the topology updating process comprising steps (11)-(13). In step (11), the topology updating message received from an adjacent node is passed to adjacent nodes. In step (12), the physical topology table is updated on the basis of the content of the topology updating message received. In step (13), the logical topology table is updated on the basis of the content of the topology updating message received.

A description will now be given, with reference to FIG. 8, of a process of restoration from a failure, wherein the topology pre-computation is executed. In FIG. 8, those steps that are the same as the steps of FIG. 7 are designated by the same numerals. The alarm message process in FIG. 8 lacks he alternate path computation process of step (6) shown in FIG. 7. That is, the determination of step (7) is made after the guard timer is started in step (5). As will be described in the following, the topology computation process shown in FIG. 7 is not necessary in the alarm message process of FIG. 8 since the topology pre-computation has been executed.

In the topology updating process shown in FIG. 8, steps (11)-(13) are the same as the corresponding steps shown in FIG. 7. After step (13) is executed, the topology computation is executed in step (18). That is, the computation of alternate paths adapted for typical failures such as those involving a path failure or a node failure is executed on the basis of the alarm message received, using an algorithm such as Dijkstra's algorithm. In this computation, the physical topology table and the logical topology table are used.

In step (14), the type of the path to be restored is identified. In the STM network, the control is then turned over to step (15). In the ATM network, the control is turned over to step (16). In step (15), the alternate path patterns are stored. That is, the patterns of path establishments that concern a given node are selected from the entire body of information obtained through the topology computation and stored in that node. In step (16), the alternate VPI is set. It will be noted that the alternate VP has a zero capacity. In step (17), the alternate VP set in step (16) is confirmed.

FIG. 9 is a diagram showing the construction of an ATM node to which the construction shown in FIG. 6 is applied. A description will now be given of how the construction shown in FIG. 6 corresponds to the construction shown in FIG. 9. The components 10 through 32 (except for the alternate path storing part 30) that concerns the STM network in the construction shown in FIG. 6 correspond to a CPU 40 shown in FIG. 9. The maintenance message transmission line 34 shown in FIG. 6 corresponds to an internal local area network (LAN) 42 shown in FIG. 9. Further, the switch SW shown in FIG. 6 corresponds to a VP-switch 44 shown in FIG. 9. The VP-switch 44 switch ATM cell according to VPI table 46. The VPI table 46 is constructed in an assumption that the zero-capacity alternate virtual path is set by the alternate VP setting part 32 shown in FIG. 6. In FIG. 9, MUX denotes a multiplexor, and DMUX a demultiplexor.

The present invention is not limited to the above described embodiments, and variations and modifications may be made without departing from the scope of the present invention.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US4679186 *26 Sep 19847 Jul 1987American Telephone And Telegraph Company, At&T Bell LaboratoriesAlternate self-routing packet switching node having fault detection capabilities
US4679189 *27 Nov 19857 Jul 1987American Telephone And Telegraph CompanyAlternate routing arrangement
US4884263 *17 Mar 198928 Nov 1989Nec CorporationPacket-switched communications network with parallel virtual circuits for re-routing message packets
US4933936 *17 Aug 198712 Jun 1990The United States Of America As Represented By The Administrator Of The National Aeronautics And Space AdministrationDistributed computing system with dual independent communications paths between computers and employing split tokens
US5084816 *12 Dec 198928 Jan 1992Bell Communications Research, Inc.Real time fault tolerant transaction processing system
US5093824 *27 Mar 19903 Mar 1992Bell Communications Research, Inc.Distributed protocol for improving the survivability of telecommunications trunk networks
US523559926 Jul 199010 Aug 1993Nec CorporationSelf-healing network with distributed failure restoration capabilities
US5627822 *11 May 19956 May 1997Siemens AktiengesellschaftMethod and circuit arrangement for disturbance-free redirection of a message cell stream onto an alternate route
US5646936 *22 Jun 19958 Jul 1997Mci CorporationKnowledge based path set up and spare capacity assignment for distributed network restoration
US5732072 *31 Aug 199524 Mar 1998Siemens AktiengesellschaftMethod for adaptive routing in a communication network
US5742820 *6 Jul 199521 Apr 1998Novell, Inc.Mechanism for efficiently synchronizing information over a network
US5805593 *26 Sep 19958 Sep 1998At&T CorpRouting method for setting up a service between an origination node and a destination node in a connection-communications network
US5883881 *30 Dec 199616 Mar 1999Mci Communications CorporationMethod for selecting preferred nodes for distributed network restoration
US6026077 *10 Nov 199715 Feb 2000Nec CorporationFailure restoration system suitable for a large-scale network
US6038212 *7 Oct 199714 Mar 2000International Business Machines CorporationMethod and system for optimizing the connection set up time in high speed communication networks for recovering from network failure
US6069894 *12 Jun 199530 May 2000Telefonaktiebolaget Lm EricssonEnhancement of network operation and performance
US6075766 *26 Nov 199613 Jun 2000Mci Communications CorporationMethod and apparatus for identifying restoral routes in a network
JPH0488738A Title not available
JPH0637783A Title not available
JPH04154242A Title not available
JPH04257143A Title not available
JPH07327048A Title not available
JPS645246A Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6530032 *23 Sep 19994 Mar 2003Nortel Networks LimitedNetwork fault recovery method and apparatus
US6600719 *4 Jan 200029 Jul 2003At&T Corp.Method and apparatus for restoring a network
US6661738 *19 Jun 20029 Dec 2003Halliburton Energy Services, Inc.Orientation and calibration of acoustic vector sensor arrays
US6671819 *6 Apr 200030 Dec 2003Bbnt Solutions LlcSystem and methods routing packets on alterate paths
US6711409 *25 Feb 200023 Mar 2004Bbnt Solutions LlcNode belonging to multiple clusters in an ad hoc wireless network
US6728205 *4 Feb 199827 Apr 2004Massachusetts Institute Of TechnologyMethod and apparatus for automatic protection switching
US6798749 *22 Nov 200028 Sep 2004Nokia CorporationMethod and system for the management of an interface in a telecommunication system
US68014962 Sep 19995 Oct 2004Cisco Technology, Inc.Network addressing scheme for reducing protocol overhead in an optical network
US685048617 Oct 20011 Feb 2005Cisco Technology, Inc.Method of reducing traffic during path restoration
US6856627 *15 Jan 199915 Feb 2005Cisco Technology, Inc.Method for routing information over a network
US697305312 Sep 20006 Dec 2005Bbnt Solutions LlcUsing direct cluster member to cluster member links to improve performance in mobile communication systems
US69755881 Jun 200113 Dec 2005Cisco Technology, Inc.Method and apparatus for computing a path through a bidirectional line switched
US6977889 *1 Sep 199920 Dec 2005Fujitsu LimitedCross-connect method and cross-connect apparatus
US6981039 *1 Aug 200127 Dec 2005Qwest Communications International, Inc.Fault management in a VDSL network
US6990063 *7 Mar 200024 Jan 2006Cisco Technology, Inc.Distributing fault indications and maintaining and using a data structure indicating faults to route traffic in a packet switching system
US699006830 Dec 200024 Jan 2006Cisco Technology, Inc.Virtual path restoration scheme using fast dynamic mesh restoration in an optical network
US70029174 Jan 200021 Feb 2006Cisco Technology, Inc.Method for path selection in a network
US700370517 Jun 200421 Feb 2006Extreme Networks, Inc.Ethernet automatic protection switching
US70128892 Nov 200014 Mar 2006Cisco Technology, Inc.Method and apparatus for controlling input rates within a packet switching system
US702739715 Feb 200111 Apr 2006Cisco Technology, Inc.Method and apparatus for accumulating and distributing traffic and flow control information in a packet switching system
US70312531 Jun 200118 Apr 2006Cisco Technology, Inc.Method and apparatus for computing a path through specified elements in a network
US70320161 Aug 200118 Apr 2006Qwest Communications International, Inc.Proactive service request management and measurement
US70466277 Sep 200116 May 2006Cisco Technology, Inc.Method and apparatus for accumulating and distributing traffic and flow control information in a packet switching system
US7050561 *19 Jul 200123 May 2006Sycamore Networks, Inc.Restoration scheme for mesh-based switching networks
US70511131 Jun 200123 May 2006Cisco Technology, Inc.Method and apparatus for computing a primary path while allowing for computing an alternate path by using a blocked list
US7054265 *17 Jul 200030 May 2006Hitachi, Ltd.Communication apparatus and communication system
US7054942 *9 Oct 199830 May 2006De La Bretoniere Ralph RogierMethod and device for protecting data communication
US70587071 Aug 20016 Jun 2006Qwest Communications International, Inc.Performance modeling in a VDSL network
US7079484 *28 Dec 200018 Jul 2006AlcatelManagement method for maintaining communications options within a private communications network
US708212410 Jul 200125 Jul 2006Cisco Technology, Inc.Method and apparatus for computing primary and alternate paths in mixed protection domain networks
US7092504 *18 Mar 200315 Aug 2006Sprint Communications Company L.P.Method and system for presenting data stored within a network component
US709267623 May 200315 Aug 2006Skyworks Solutions, Inc.Shared functional block multi-mode multi-band communication transceivers
US71066932 Nov 200012 Sep 2006Cisco Technology, Inc.Method and apparatus for pacing the flow of information sent from a device
US71204567 Nov 200110 Oct 2006Bbn Technologies Corp.Wireless terminals with multiple transceivers
US7126921 *20 Mar 200224 Oct 2006Tropic Networks Inc.Packet network providing fast distribution of node related information and a method therefor
US71341351 Aug 20017 Nov 2006Qwest Communications International Inc.Fault management in a VDSL network
US7142505 *29 Jul 200328 Nov 2006At&T Corp.Method and apparatus for restoring a network
US7155120 *30 Jul 200126 Dec 2006Atrica Israel Ltd.Link level network protection path calculation mechanism for use in optical networks
US7188280 *29 Aug 20016 Mar 2007Fujitsu LimitedProtecting route design method in a communication network
US720010416 May 20013 Apr 2007Cisco Technology, Inc.Method for restoring a virtual path in an optical network using 1+1 protection
US7206281 *3 May 200217 Apr 2007Ciena CorporationCalculating physical routes in a communication network
US72191241 Aug 200115 May 2007Qwest Communications International Inc.Provisioning system and method for auto-discovering customer premises equipment in activating xDSL
US7274869 *29 Nov 199925 Sep 2007Nokia Networks OySystem and method for providing destination-to-source protection switch setup in optical network topologies
US7292686 *5 Sep 20026 Nov 2007Hewlett-Packard CompanyExchange node
US73018951 Feb 200627 Nov 2007Cisco Technology, Inc.Virtual path restoration scheme using fast dynamic mesh restoration in an optical network
US735269216 May 20011 Apr 2008Cisco Technology, Inc.Resource reservation scheme for path restoration in an optical network
US7388827 *23 Oct 200217 Jun 2008Eci Telecom Ltd.High speed dissemination of failure information in mesh networks
US742821220 May 200223 Sep 2008Cisco Technology, Inc.Best effort technique for virtual path restoration
US7457233 *15 Jul 199925 Nov 2008Juniper Networks, Inc.Method and apparatus for fast reroute in a connection-oriented network
US74641641 Aug 20019 Dec 2008Qwest Communications International, Inc.Linking order entry process to realtime network inventories and capacities
US74671931 Aug 200116 Dec 2008Qwest Communications International IncManagement of virtual and physical network inventories
US74775947 Jun 200113 Jan 2009Cisco Technology, Inc.Method for restoring a virtual path in an optical network using 1:N protection
US7490165 *18 Jul 200110 Feb 2009Cisco Technology, Inc.Method and apparatus for computing a path in a system with nodal and link diverse constraints
US7496294 *30 Aug 200124 Feb 2009Mitsubishi Denki Kabushiki KaishaOptical multi-branch communication system
US750231329 Dec 200010 Mar 2009Cisco Technology, Inc.Virtual path restoration scheme using fast dynamic mesh restoration in an optical network
US7518985 *26 Apr 200514 Apr 2009Hitachi Communication Technologies, Ltd.Communication apparatus and communication system
US7551553 *26 Oct 200623 Jun 2009At&T Intellectual Property, Ii, L.P.Method and apparatus for restoring a network
US7593321 *4 Aug 200322 Sep 2009Cisco Technology, Inc.Method and system for a local and fast non-disruptive path switching in high speed packet switching networks
US760348115 Jul 200313 Oct 2009Novell, Inc.Dynamic routing through a content distribution network
US761658412 Nov 200410 Nov 2009Cisco Technology, Inc.Minimizing single points of failure in paths with mixed protection schemes
US7633854 *9 Feb 200515 Dec 2009Cisco Technology, Inc.Method for routing information over a network
US769307923 Dec 20046 Apr 2010Qwest Communications International, Inc.Proactive repair process in the xDSL network (with a VDSL focus)
US7729337 *29 Dec 20001 Jun 2010Cisco Technology, Inc.Protocol for the determination of network topology
US7764596 *25 Jun 200127 Jul 2010Cisco Technology, Inc.Method for restoring a virtual path in an optical network using dynamic unicast
US781757031 Dec 200619 Oct 2010At&T Intellectual Property Ii, L.P.Method and apparatus for providing automated diagnostics of networks using multiple virtual circuits
US784380821 Oct 200830 Nov 2010Juniper Networks, Inc.Method and apparatus for fast reroute in a connection-oriented network
US78537159 Dec 200814 Dec 2010Cisco Technology, Inc.Method and apparatus for computing a path in a system with nodal and link diverse constraints
US79168557 Jan 200529 Mar 2011Cisco Technology, Inc.System and method for storing and restoring communication dialog
US7933266 *20 Apr 200426 Apr 2011Cisco Technology, Inc.Configurable network router
US7940648 *2 Mar 200410 May 2011Cisco Technology, Inc.Hierarchical protection switching framework
US7995485 *31 Dec 20069 Aug 2011At&T Intellectual Property Ii, L.P.Method and apparatus for providing automated diagnostics of networks
US80787563 Jun 200313 Dec 2011Cisco Technology, Inc.Computing a path for an open ended uni-directional path protected switched ring
US813601223 Mar 200713 Mar 2012Infovista SaMethod and system for updating topology changes of a computer network
US836480115 Dec 200829 Jan 2013Qwest Communications International Inc.Management of virtual and physical network inventories
US8406121 *19 Sep 200526 Mar 2013Nokia Siemens Networks Gmbh & Co. KgMethod for error detection in a packet-based message distribution system
US842796224 Mar 200823 Apr 2013Cisco Technology, Inc.Control of inter-zone/intra-zone recovery using in-band communications
US843279027 Feb 201130 Apr 2013Cisco Technology, Inc.Hierarchical protection switching framework
US8489721 *30 Dec 200816 Jul 2013Symantec CorporationMethod and apparatus for providing high availabilty to service groups within a datacenter
US8526298 *21 Oct 20103 Sep 2013Juniper Networks, Inc.Method and apparatus for fast reroute in a connection-oriented network
US8619785 *28 Apr 200931 Dec 2013Ciena CorporationPre-computing alternate forwarding state in a routed ethernet mesh network
US8750141 *5 Nov 200910 Jun 2014Rockstar Consortium Us LpDistributed connection establishment and restoration
US87625686 Jul 200124 Jun 2014Cisco Technology, Inc.Method and apparatus for inter-zone restoration
US20070115810 *23 Jan 200724 May 2007Telecommunications Research LaboratoriesDistributed preconfiguration of spare capacity in closed paths for network restoration
US20070206583 *14 Feb 20076 Sep 2007Christopher James NasonMethod of accelerating control link loss detection
US20110090784 *21 Oct 201021 Apr 2011Juniper Networks, Inc.Method and apparatus for fast reroute in a connection-oriented network
CN1981463B22 Jun 200416 Nov 2011中兴通讯股份有限公司Business connection set-up and business recovering protection method in optical network
EP1768281A1 *22 Jun 200428 Mar 2007ZTE CorporationA method for service connection setup and service resume protection in optical network
EP1830492A1 *1 Dec 20045 Sep 2007ZTE CorporationRecovering method in a complex optical network
WO2005125056A1 *22 Jun 200429 Dec 2005Zte CorpA method for service connection setup and service resume protection in optical network
WO2006058458A1 *1 Dec 20048 Jun 2006Zte CorpRecovering method in a complex optical network
WO2007118957A223 Mar 200725 Oct 2007Infovista SaMethod and system for updating topology changes of a computer network
Classifications
U.S. Classification370/218, 370/228, 370/255, 709/239, 370/400, 340/2.9
International ClassificationH04M3/12, H04Q3/00, H04L12/24, H04M3/22, H04M3/10
Cooperative ClassificationH04Q3/0079, H04M3/12, H04L41/12, H04M3/2254, H04Q2213/13167, H04Q2213/13141, H04L41/0663, H04M3/10
European ClassificationH04L41/12, H04M3/22N, H04Q3/00D4F1, H04L12/24D3
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